It's one more rule, I really don't think it's that big of a deal to keep track of, and a little extra work on the side-lines. The upside is that it makes for a more tactically nuanced contest, and all the players get the same amount of court-time.
My biggest reservation about the BM format is that it's obvious that some players get to play hardly at all, which isn't fun.
Given that this is a friendly match, it seems an appropriate moment to trial a rule-change that might improve the BM format.
What about you have to change two out of a line every chukker. (every fifteen minutes) Six chukkers, everyones a winner?
What about you have to change two out of a line every chukker. (every fifteen minutes) Six chukkers, everyones a winner?